As fuel for an ignitor such as a cigarette lighter, there is generally used fuel alcohol such as ethyl alcohol, fuel benzine such as petroleum benzine, or liquefied gas fuel such as butane gas, propane gas or the like.
Performance, convenience of handling and design properties of ignitors differ depending on the kind of fuel used.
For example, in the case of fuel benzine which is a mixture of petroleum benzine series hydrocarbons different in boiling point, benzine components lower in boiling point are mainly volatilized at the beginning of use and the volatile components change to those of higher boiling points. Accordingly, the composition of the fuel remaining in the ignitor changes with the burning time, which causes change in the flame length. The same is the case with gasoline. Further since benzine and gasoline are high in volatility, a closed structure for suppressing volatilization of fuel liquid from the fuel storage portion and/or the wick is required in an ignitor where benzine or gasoline is used as the fuel liquid. When closure of the closed structure is insufficient, the fuel liquid is soon lost and the fuel liquid must be frequently replenished. Further some people are not fond of the peculiar odor of benzine and gasoline.
In the case of liquefied gas fuel, the pressure of gas is high in the operating temperature range of the ignitor and accordingly the fuel reservoir must be pressure-resistant. Further, the flame length changes with change in the gas pressure which logarithmically largely changes with change in the temperature, and large fluctuation in the flame length with change in the temperature has been a problem with a gas ignitor. In order to overcome this problem, the fuel supply system of the ignitor must be provided with a special temperature correction means, which complicates the structure of the ignitor and adds to the cost.
The alcohol fuel mainly comprises monovalent lower alcohol such as ethyl alcohol, methyl alcohol, propyl alcohol or the like and is liquid at normal temperatures and is relatively low in vapor pressure. Accordingly, an alcohol-fueled ignitor need not be pressure-resistant in its fuel reservoir, and the fuel storage portion and/or the wick have only to be closed to such an extent that volatilization of the alcohol fuel can be suppressed. Accordingly, the alcohol-fueled ignitor can be simpler in structure and can be manufactured at lower cost.
In the alcohol-fueled ignitor, the alcohol fuel is supplied from the fuel reservoir to the burning portion through a wick which is of an open cell cellular material or of a bundle of thin fibers. The alcohol fuel is drawn up from the lower end portion of the wick and supplied to the upper end portion of the wick through the open cell or the fine spaces between the fibers by capillarity.
More specifically, the wick is formed by twisting fibers, by bundling glass fibers, or by wrapping a bundle of glass fibers by cotton yarns and fixing the cotton yarns to the glass fiber bundle by winding thin metal wire around the cotton yarns.
In an ignitor in accordance with a prior art in which fuel liquid containing therein alcohol as a main component thereof is used, the structure of the wick should be as simple as possible so that the quality of the wick is uniform and the wicks can be manufactured at low cost since the structure of the wick is related to the burning properties of the ignitor. For this purpose, it is preferred that the wick is formed of glass fibers or ceramic fibers.
In an ignitor using such a wick, an initial flame length just after the fuel is ignited, change of the flame length, the maximum flame length and the like vary depending upon the material, dimensions and shape of the wick, and accordingly the wick should be arranged to meet desired properties of the ignitor.
That is, in the alcohol-fueled ignitor such as a cigarette lighter, fuel on the surface of the wick starts burning with flame upon ignition thereof. The flame length at this time is taken as an initial flame length.
Then the wick is heated by the burning and the amount of fuel volatilizing from the surface of the wick increases, whereby the flame length increases. However increase in temperature at the surface of the wick gets equilibrated and stops as the burning continues, and increase in the flame length is saturated and the flame length reaches a saturated flame length. As fuel on the surface of the wick burns and consumes, fuel inside the wick is dispersed toward the surface of the wick and fuel in the fuel reservoir is drawn up through the lower end portion of the wick.
When consumption of fuel at the surface of the wick balances supply of fuel from the inside of the wick and supply of fuel from the fuel reservoir, burning continues in the equilibrated state and the flame length is stabilized. To the contrast, when fuel consumption at the surface of the wick exceeds fuel supply from the inside of the wick, the flame length becomes shorter than the initial flame length and gets equilibrated at a level according to the fuel supply or the flame is quenched.
In view of the foregoing observations and description, the primary object of the present invention is to provide a structure of a burning portion of an alcohol-fueled ignitor which is suitable for obtaining optimal burning.
In the case of a cigarette lighter, preferably the flame length is initially at least about 20 mm and increases to about 25 mm in 10 seconds or so. Further it is preferred that the saturated flame length, that is, the flame length when the wick is heated to an equilibrium temperature, be about 60 mm to 70 mm (about 50 mm to 70 mm according to the purpose of the ignitor) at most. In order to meet these requirements, the wick should have the capability of drawing up fuel liquid and retaining the same and should be heat-resistant. Further, the wick should be of such a form that the aforesaid burning conditions can be realized.